Showing papers on "Schottky diode published in 1998"

Schottky barrier detectors for visible-blind ultraviolet detection

Abstract: The invention concerns the fabrication and characterization of vertical geometry transparent Schottky barrier ultraviolet detectors based on n- /n+ -GaN and AlGaN structures grown over sapphire substrates. Mesa geometry devices of different active areas were fabricated and characterized for spectral responsitivity, speed and noise characteristics. The invention also concerns the fabrication and characterization of an 8×8 Schottky barrier photodiode array on GaN with a pixel size of 200 μm by 200 μm.

Multilayer Thermionic Refrigeration

Abstract: A new method of refrigeration is proposed. Efficient cooling is obtained by thermionic emission of electrons over Schottky barriers between metals and semiconductors. Since the barriers have to be thin, each barrier can have only a small temperature difference $(\ensuremath{\sim}1\mathrm{K})$. Macroscopic cooling is obtained with a multilayer device. The same device is also an efficient generator of electrical power. A complete analytic theory is provided.

Trench-gated MOSFET with bidirectional voltage clamping

Abstract: The gate of a MOSFET is located in a lattice of trenches which define a plurality of cells. Most of the cells contain a MOSFET, but a selected number of the cells at predetermined locations in the lattice contain either a PN diode or a Schottky diode. The PN and Schottky diodes are connected in parallel with the channels in the MOSFET cells, with their anodes tied to the anode of the parasitic diodes in the MOSFET cells and their cathodes tied to the cathode of the parasitic diodes. When the MOSFET is biased in the normal direction (with the parasitic diode reverse-biased), the PN diodes provide a predictable breakdown voltage for the device and ensure that avalanche breakdown occurs at a location away from the trench gate where the hot carriers generated by the breakdown cannot damage the oxide layer which lines the walls of the trench. When the device is biased in the opposite direction, the Schottky diodes conduct and thereby limit charge storage at the PN junctions in the diode and MOSFET cells. This reduces the power loss in the MOSFET and improves the reverse recovery characteristics of the device when its bias is switched back to the normal direction.

Design considerations and experimental analysis of high-voltage SiC Schottky barrier rectifiers

Abstract: Practical design of high-voltage SiC Schottky rectifiers requires an understanding of the device physics that affect the key performance parameters. Forward characteristics of SiC Schottky rectifiers follow thermionic emission theory and are relatively well understood. However, the reverse characteristics are not well understood and have not been experimentally investigated in-depth. In this paper we report the analysis and experimental results of both the forward and reverse characteristics of high-voltage SiC Schottky rectifiers. Ti and Ni Schottky rectifiers with boron implant edge termination were fabricated on n-type 4H SiC samples. Ni Schottky rectifiers fabricated on a 13-/spl mu/m thick 3.5/spl times/10/sup 15/ cm/sup -3/ epilayer have a current density of 100 A/cm/sup 2/ at approximately 2 V forward bias and a reverse leakage current density of less than 0.1 A/cm/sup 2/ at a reverse bias of 1720 V. The reverse leakage current is observed to depend on device area, Schottky barrier height, electric field at the metal-semiconductor interface, and temperature (a decreasing temperature dependence with increasing reverse bias). In addition. the reverse leakage current magnitude is larger and the electric field dependence is stronger than predicted by thermionic emission and image-force barrier height lowering. This suggests the reverse leakage current is due to a combination of thermionic field emission and field emission.

Schottky barrier engineering in III-V nitrides via the piezoelectric effect

Abstract: A method for enhancing effective Schottky barrier heights in III–V nitride heterostructures based on the piezoelectric effect is proposed, demonstrated, and analyzed. Two-layer GaN/AlxGa1−xN barriers within heterostructure field-effect transistor epitaxial layer structures are shown to possess significantly larger effective barrier heights than those for AlxGa1−xN, and the influence of composition, doping, and layer thicknesses is assessed. A GaN/Al0.25Ga0.75N barrier structure optimized for heterojunction field-effect transistors is shown to yield a barrier height enhancement of 0.37 V over that for Al0.25Ga0.75N. Corresponding reductions in forward-bias current and reverse-bias leakage are observed in current–voltage measurements performed on Schottky diodes.

Comparison of raised and Schottky source/drain MOSFETs using a novel tunneling contact model

Abstract: We present, for the first time, a physical contact tunneling model that is critical for studying the increasingly important contact behaviour in future scaled CMOS. The tunneling processes are self-consistently treated with all current transport in the semiconductor. With this new model, we compared the performance of raised S/D and Schottky S/D MOSFETs. Both raised S/D and Schottky S/D MOSFETs can be designed to give good short-channel characteristics. Our analyses show that despite the lower sheet resistance of the Schottky S/D MOSFETs, contact resistance could be large due to finite Schottky barrier height. A lower barrier height contact material should be used to minimize the contact resistance.

The role of the tunneling component in the current–voltage characteristics of metal-GaN Schottky diodes

Abstract: The temperature dependence of the current–voltage characteristics of Ni–GaN Schottky barriers have been measured and analyzed. It was found that the enhanced tunneling component in the transport current of metal-GaN Schottky barrier contacts is a likely explanation for the large scatter in the measured Richardson constant.

The electronic conduction mechanism in barium strontium titanate thin films

Abstract: In the literature, the Schottky emission equation is widely used to describe the conduction mechanism in perovskite-type titanate thin films. Though the equation provides a good fit to the leakage current data, the extracted values of the Richardson and dielectric constants are inconsistent with their experimental values. In this work, a modified Schottky equation is applied. This equation resolves the difficulties associated with the standard Schottky equation. Also, the electronic mobility in thin films of barium strontium titanate is reported.

Multilayer thermionic refrigerator and generator

Abstract: A new method of refrigeration is proposed. Cooling is obtained by thermionic emission of electrons over periodic barriers in a multilayer geometry. These could be either Schottky barriers between metals and semiconductors or else barriers in a semiconductor superlattice. The same device is an efficient power generator. A complete theory is provided.

Effects of thermal annealing on the indium tin oxide Schottky contacts of n-GaN

Abstract: In this work indium tin oxide (ITO) films were prepared using electron beam evaporation to form Schottky contacts on n-type GaN films. The thermal stability of ITO on n-type GaN was also investigated by annealing the samples at various temperatures. In addition, current–voltage (I–V) measurements were taken to deduce the Schottky barrier heights. Owing to the large series resistance, the Norde method was used to plot the F(V)–V curves and the effective Schottky barrier heights were determined as well. The effective Schottky barrier heights were 0.68, 0.88, 0.94, and 0.95 eV for nonannealed, 400, 500, and 600 °C annealed samples, respectively. Results presented herein indicate that an increase of the barrier heights may be attributed to the formation of an interfacial layer at the ITO/GaN interface after annealing.

Design and Experiments of a High-Conversion-Efficiency

Abstract: A high-efficiency rectenna element has been designed and tested at 5.8 GHz for applications involving microwave- power transmission. The dipole antenna and filtering circuitry are printed on a thin duroid substrate. A silicon Schottky- barrier mixer diode with a low breakdown voltage is used as the rectifying device. The rectenna element is tested inside a waveguide simulator and achieves an RF-to-dc conversion efficiency of 82% at an input power level of 50-mW and 327- load. Closed-form equations are given for the diode efficiency and input impedance as a function of input RF power. Measured and calculated efficiency results are in good agreement. The antenna and circuit design are based on a full-wave electromagnetic simulator. Second harmonic power levels are 21 dB down from the fundamental input power.

Visible-blind GaN Schottky barrier detectors grown on Si(111)

Abstract: We report novel GaN detectors grown by molecular beam epitaxy on Si(111) substrates. Wurtzite structure epitaxial GaN exhibits room-temperature photoluminescence with a band-edge-related emission width as narrow as 7 nm and intensities comparable to high quality layers grown on sapphire by metalorganic chemical vapor deposition. Spectral response of lateral geometry Schottky detectors shows a sharp cutoff at 365 nm with peak responsivities of ∼0.05 A/W at 0 V, and ∼0.1 A/W with a −4 V bias. The dark current is ∼60 nA at −2 V bias. The noise equivalent power is estimated to be 3.7×10−9 W over the response bandwidth of 2.2 MHz.

Minority carrier diffusion length and lifetime in GaN

Abstract: Electron beam induced current measurements on planar Schottky diodes on undoped GaN grown by metalorganic chemical vapor deposition are reported. The minority carrier diffusion length of 0.28 μm has been measured, indicating minority carrier lifetime of 6.5 ns. The tapping mode atomic force microscopy imaging of the surfaces and scanning electron microscopy of the cross sections have been used to characterize the linear dislocations and columnar structure of the GaN. The possible influence of recombination on the extended defects in GaN on the minority carrier diffusion length and lifetime is discussed, and contrasted to other recombination mechanisms.

Development of a silicon carbide radiation detector

Abstract: The radiation detection properties of semiconductor detectors made of 4H silicon carbide were evaluated. Both Schottky and p-n junction devices were tested. Exposure to alpha particles from a /sup 238/Pu source led to robust signals from the detectors. The resolution of the Schottky SiC detector was 5.8% (FWHM) at an energy of 294 keV, while that of the p-n junction was 6.6% (FWHM) at 260 keV. No effect of temperature in the range of 22 to 89/spl deg/C was observed on the characteristics of the /sup 238/Pu alpha-induced signal from the SiC detector. In addition, testing in a gamma field of 10,000 rad-Si h/sup -1/ showed that the alpha-induced signal was separable from the gamma signal.

Silicon carbide power devices

Abstract: The more and more demanding requirements of the power device users bring the silicon technology very close to its own physical limits. Silicon carbide (SiC) appears today as the only semiconductor having the capability for significantly improving the ratings of major power components (such as high voltage Schottky rectifiers), indeed for creating novel devices for new applications. The choice of SiC comes from superior physical properties, an existing substrate commercialization, and an experimental confirmation of several potentialities (at high voltage, temperature, or frequency) via demonstrative prototypes. However, such a young technology still suffers from a too poor quality of the available basic materials, and from the fabrication step immaturity, delaying the SiC power electronics emergence.

Electron diffusion length and lifetime in p-type GaN

Abstract: We report on electron beam induced current and current–voltage (I–V) measurements on Schottky diodes on p-type doped GaN layers grown by metal organic chemical vapor deposition. A Schottky barrier height of 0.9 eV was measured for the Ti/Au Schottky contact from the I–V data. A minority carrier diffusion length for electrons of (0.2 ± 0.05) µm was measured for the first time in GaN. This diffusion length corresponds to an electron lifetime of approximately 0.1 ns. We attempted to correlate the measured electron diffusion length and lifetime with several possible recombination mechanisms in GaN and establish connection with electronic and structural properties of GaN.

The Schottky energy barrier dependence of charge injection in organic light-emitting diodes

Abstract: We present device model calculations of the current–voltage (I–V) characteristics of organic diodes and compare them with measurements of structures fabricated using MEH-PPV. The structures are designed so that all of the current is injected from one contact. The I–V characteristics are considered as a function of the Schottky energy barrier to charge injection from the contact. Experimentally, the Schottky barrier is varied from essentially zero to more than 1 eV by using different metal contacts. A consistent description of the device I–V characteristics is obtained as the Schottky barrier is varied from small values, less than about 0.4 eV, where the current flow is space-charge limited to larger values where it is contact limited.

Ni and Ti Schottky barriers on n-AlGaN grown on SiC substrates

Abstract: The electrical characteristics of Ni and Ti Schottky barriers on n-Al0.15Ga0.85N on SiC were investigated. We report that the barrier height for Ni on n-Al0.15Ga0.85N was about 1.26 eV and about 1 eV or less for Ti. These barrier heights are about 0.3–0.4 eV larger than those for Ni and Ti on n-GaN, which are in good agreement with Schottky model predictions.

Semiconductor component with metal-semiconductor junction with low reverse current

Abstract: The semiconductor component, such as a Schottky diode with a low leakage current, has a metal-semiconductor junction between a first metal electrode and the semiconductor. The semiconductor, which is of a first conductivity type, has a defined drift path and a plurality of supplementary zones of a second conductivity type extending from the semiconductor surface into the drift path. A number of foreign atoms in the supplementary zones is substantially equal to a number of foreign atoms in intermediate zones surrounding the supplementary zones and the number of foreign atoms does not exceed a number corresponding to a breakdown charge of the semiconductor.

Conduction power loss in MOSFET synchronous rectifier with parallel-connected Schottky barrier diode

Abstract: The conduction power loss in an MOSFET synchronous rectifier with a parallel-connected Schottky barrier diode (SBD) was investigated. It was found that the parasitic inductance between the MOSFET and SBD has a large effect on the conduction power loss. This parasitic inductance creates a current that is shared by the two devices for a certain period and increases the conduction power loss. If conventional devices are used for under 1 MHz switching, the advantage of the low on-resistance MOSFET will almost be lost. To reduce the conduction loss for 10 MHz switching, the parasitic inductance must be a subnanohenley.

Green electroluminescence from Er-doped GaN Schottky barrier diodes

Abstract: Visible lightelectroluminescence(EL) has been obtained from Er-doped GaN Schottky barrierdiodes. The GaN was grown by molecular beam epitaxy on Si substrates using solid sources (for Ga, and Er) and a plasma source for N 2 . Al was utilized for both the Schottky (small-area) and ground (large-area) electrodes. Strong green light emission was observed under reverse bias, with weaker emission present under forward bias. The emission spectrum consists of two narrow green lines at 537 and 558 nm and minor peaks at 413 and at 666/672 nm. The green emission lines have been identified as Er transitions from the 2 H 11/2 and 4 S 3/2 levels to the 4 I 15/2 ground state and the blue and red peaks as the 2 H 9/2 and 4 F 9/2 Er transitions to the same ground state. The reverse bias EL intensity was found to increase linearly with bias current.

Electronic characteristics of the srbi2ta2o9-pt junction

Abstract: The voltage and film composition dependence of leakage currents of ferroelectric SrBi2Ta2O9 thin films, sandwiched between Pt has been studied. Schottky emission dominated the leakage current at voltages above the ohmic conduction regime, while space charge limited currents (SCLC), for which the observed temperature dependence is correctly predicted in Rose’s theory, appeared to dominate the leakage current in high conductivity SrBi2Ta2O9 thin films including bismuth-excess samples. A consequence of the latter was the observation of negative differential resistivity in high conductivity SrBi2Ta2O9 thin films. X-ray photoemission spectroscopy depth profiling indicated that Bi has diffused into the ferroelectric–metal interface and also influenced the electronic conduction mechanism of the ferroelectric capacitors. Confirmation of this was found through the current–voltage dependence of Pt/SrBi2Ta2O9/Bi, which is compatible with space charge limited currents. The theory of Rose was successfully applied to t...

Current transport mechanisms in GaN-based metal–semiconductor–metal photodetectors

Abstract: We report on the current transport mechanisms dominant at the Schottky interface of metal–semiconductor–metal photodetectors fabricated on single-crystal GaN, with active layers of 1.5 and 4.0 μm thickness. We have modeled transport in the 1.5 μm devices using thermionic emission theory, and in the 4.0 μm devices using thermionic field emission theory. We have obtained a good fit to the experimental data. We hypothesize that traps in the GaN are related to a combination of surface defects (possibly threading dislocations), and deep-level bulk states that are within a tunneling distance of the interface. A simple qualitative model is presented.

JUNCTION TERMINATION FOR SiC SCHOTTKY DIODE

Abstract: A semiconductor diode structure with a Schottky junction, where a metal contact (2) and a silicon carbide semiconducting layer (1) of a first conducting type form said junction and where the edge of the junction exhibits a junction termination divided into a transition belt (TB) having gradually increasing total charge or effective sheet charge density closest to the metal contact and a Junction Termination Extension (JTE) outside the transition belt, said JTE having a charge profile with a stepwise or uniformly decreasing total charge or effective sheet charge density from an initial value to a zero or almost zero total charge at the outermost edge of the termination following a radial direction from the center part of the JTE towards the outermost edge of the termination. The purpose of the transition belt is to reduce the electric field concentration at the edge of the metal contact of the Schottky diode, while the purpose of the junction termination extension is to control the electric field at the periphery of the diode.

Scalable MOS field effect transistor

Abstract: A field effect transistor and method for making is described incorporating self aligned source and drain contacts with Schottky metal-to-semiconductor junction and a T-shaped gate or incorporating highly doped semiconductor material for the source and drain contacts different from the channel material to provide etch selectivity and a T-shaped gate or incorporating a metal for the source and drain contacts and the oxide of the metal for the gate dielectric which is self aligned. The invention overcomes the problem of self-aligned high resistance source/drain contacts and a high resistance gate electrode for submicron FET devices which increase as devices are scaled to smaller dimensions.

Experimental investigation of dependence of electrical characteristics on device parameters in trench MOS barrier Schottky diodes

Abstract: Measurements of forward and reverse electrical characteristics of trench MOS barrier Schottky diodes with various device parameters reveal that the resistivity and width of the mesa region are the main parameters which affect device characteristics. An on/off current ratio of two orders is obtained.

Two-dimensional numerical simulation of Schottky barrier MOSFET with channel length to 10 nm

Abstract: We present simulation results of a silicon-based metal-oxide-semiconductor field-effect transistor (MOSFET), which has a structure similar to that of a conventional MOSFET, but the source and drain regions are now entirely replaced by metals. By using abrupt metal/silicon Schottky junctions, short-channel effects are avoided. Based on a few commonly used physical assumptions, we have calculated the transistor characteristics, and we find that this new three-terminal transistor can offer gain and impedance isolation, desirable for logic circuit applications.

Laser diode driving method and circuit

Abstract: In a laser diode driving method, a bias current set about the light emission threshold current of a laser diode, and a pulse current for causing the laser diode to emit light are adjusted in accordance with the ambient temperature. The laser diode is driven by a current prepared by superposing the bias current and the pulse current, thereby controlling the optical output and extinction ratio of the laser diode at a constant level. A laser diode driving circuit is also disclosed.

Schottky diode with dielectric trench

Abstract: An improved diode or rectifier structure and method of fabrication is disclosed involving the incorporation in a Schottky rectifier, or the like, of a dielectric filled isolation trench structure formed in the epitaxial layer adjacent the field oxide layers provided at the edge of the active area of the rectifier, for acting to enhance the field plate for termination of the electric field generated by the device during operation. The trench is formed in a closed configuration about the drift region and by more effectively terminating the electric field at the edge of the drift region the field is better concentrated within the drift region and acts to better interrupt reverse current flow and particularly restricts leakage current at the edges.